Psychological interventions for adults who are overweight or obese

Abstract

This is a protocol for a Cochrane Review (Intervention). The objectives are as follows:

To assess the effects of psychological interventions for the treatment of overweight and obese adults. Specific objectives are to examine the efficacy of:

1. All psychological therapies versus minimal or no intervention;

2. All psychological therapies versus an active diet and/or exercise intervention;

3. Behavioural psychological therapies (first, second or third wave) versus other psychological interventions.

Secondary objectives are to examine if the magnitude of intervention effects (objectives 1, 2, and 3) for the primary outcome of BMI are modified by particular intervention characteristics (length of follow‐up), or participant characteristics (degree of excess weight). We also plan to investigate whether the effects of behavioural therapy are modified by the type of behaviour intervention (first, second or third wave).

Background

Description of the condition

Overweight and obesity are defined as "conditions of abnormal or excessive fat accumulation in adipose tissue, to the extent that health may be impaired" (WHO 1998). These conditions are operationally defined as a body mass index (BMI), weight in kilograms divided by the square of height in metres (kg/m²), of ≥ 25 kg/m² and ≥ 30 kg/m² respectively (WHO 1998). The World Health Organization (WHO) estimates that in 2014, 39% of adults were overweight (38% men and 40% women) and 13% were obese (11% men and 15% women). Worldwide rates of overweight and obesity in adults continue to rise. Rates of extreme obesity are rising most quickly (WHO 2014). Although the prevalence of overweight and obesity are highest in developed countries, rates in developing countries are rising dramatically as income, urbanisation, and processed food availability increase (WHO 2014). In higher‐income countries, obesity rates are highest among the poor and those living in rural areas. In contrast, obesity rates in lower‐income countries are highest among those living in urban and more affluent areas. The risk of obesity for women in low‐ and lower‐middle‐income countries is almost double that of men. Rates are similar for men and women in high‐income countries (WHO 2014).

Excess weight is associated with a range of negative biopsychosocial outcomes; the higher the weight, the greater the risk. The metabolic correlates of overweight and obesity include higher blood pressure, raised cholesterol and triglycerides levels, and greater insulin resistance. Consequently, overweight and obesity are associated with increased risk of cardiovascular disease, type 2 diabetes mellitus, and some cancers (e.g., breast, colon, prostate). Excess weight is also associated with a range of musculoskeletal, respiratory, skin, and fertility conditions that impair health‐related quality of life (Guh 2009; WHO 2000; WHO 2014). Research examining the psychosocial consequences of overweight and obesity has focused almost exclusively on developed countries. Studies examining the psychological correlates of obesity in the community report mixed findings; however, on balance, they suggest that women who are obese are vulnerable to symptoms of depression (including suicidal ideation) and low self‐esteem (Luppino 2010). Results are more consistent in those seeking weight loss treatment. Overweight and obese treatment‐seekers demonstrate higher rates of psychopathology, including mood disorders (depression, low self‐esteem, anxiety) and eating disorders (binge eating disorder, night eating syndrome, body image dissatisfaction), as well as impaired health‐related quality of life (Fontaine 2001; Jia 2005; Wadden 2002b). Heavier individuals are also at increased risk of discrimination in employment, health care, education, the media, and in interpersonal relationships (Puhl 2003). Combined, these negative biopsychosocial outcomes result in significant impairments in health‐related quality of life (WHO estimates that 35.8 million (2.3%) of global disease‐adjusted life years (DALYs) are caused by overweight or obesity) and loss of productivity (Fontaine 2001; Robroek 2010). Further, management of weight‐related comorbidities places a significant burden on healthcare systems (Colagiuri 2010; Hammond 2010; Müller‐Riemenschneider 2008; Wang 2011; WHO 2000).

Traditionally, overweight and obesity were thought to be a consequence of an individual’s poor health choices and behaviours resulting in excess energy balance (Skender 1996; Spiegelman 2001). Thus, early prevention and treatment efforts were targeted at individual behaviour change (Kremers 2010; Lemmens 2008; Shaw 2005; Shaw 2006; Thomas 2007). There is now improved understanding of the complexity of factors contributing to excess energy balance and weight gain. These include: individual and social psychology, individual physical activity and the activity environment, food consumption and production, human and individual physiology (Vandenbroeck 2007). As a result of this improved understanding, prevention and intervention efforts are changing to encompass a wider range of contributing factors (Beauchamp 2014; Franz 2007; Kremers 2010; Lemmens 2008).

The high and increasing prevalence of overweight and obesity highlights the need for prevention efforts. Despite considerable research and intervention efforts targeting obesity prevention, the rate of excess weight continues to rise. Successful prevention efforts aim to first slow, then halt, then reverse increasing rates of overweight and obesity. Therefore, overweight and obesity rates will remain high for some time, even if prevention efforts are successful. Thus, effective treatment approaches are required.

Description of the intervention

Overweight and obesity are treated using 'lifestyle' (diet, exercise), medical (pharmacological), and surgical interventions. Dietary interventions targeting reduced energy and/or relative macronutrient intake result in small weight losses in the short term with weight typically regained in the longer term (Hession 2009; Thomas 2007). Very low energy diets result in larger weight losses, but weight is typically regained (Franz 2007; Mann 2007). Exercise interventions targeting increased energy expenditure via cardiovascular and/or resistance training result in small weight losses, and result in marginal improvements in weight loss when combined with dietary interventions (Jakicic 2001; Shaw 2006). A number of pharmacological treatments have been shown to improve weight loss outcomes (Franz 2007; Padwal 2003). However, few are currently approved for use in the treatment of obesity. Although surgical interventions are becoming increasingly popular and produce the most substantial and sustained weight loss, they also carry the most risk (Colquitt 2014).

While psychological interventions are often used in combination with medical interventions (Douketis 2005), the majority of the research examining psychological interventions examines these interventions used in isolation or in combination with 'lifestyle' interventions (Sarwer 2014). A range of psychological interventions has been used in the treatment of overweight and obesity. These interventions have typically been adapted from those designed to treat mental health conditions. The overarching objective of this type of intervention is to reduce the psychological barriers to health behaviour change (Shaw 2005). Which barriers are targeted, and via which mechanisms, vary across types of psychological intervention.

Treatment delivery settings (e.g. hospital, community), delivery modes (e.g. face to face, telephone, online), delivery agent (e.g., psychologist, other health professional, lay person), and intensity and duration, have varied considerably across these interventions (Shaw 2005). Greater intensity and duration have resulted in greater weight loss and weight maintenance respectively (Franz 2007). There are few other consistent findings regarding the impact of these treatment characteristics on treatment outcomes.

How the intervention might work

Psychological interventions for overweight and obesity aim to reduce the psychological barriers to health behaviour change and maintenance. The behavioural, cognitive, social and emotional variables that are conceptualised as barriers and therefore targeted in treatment vary depending on the theoretical underpinnings of the intervention. The majority of psychological interventions for overweight and obesity are cognitive behaviourally based, and are typically used in combination with lifestyle interventions (Shaw 2005). There are three 'waves' of cognitive behavioural interventions. First wave or behaviour therapies target modification of the behaviours and the antecedents and consequences hypothesised to be maintaining a positive energy balance (Wadden 2002a; Wing 2001). Second wave or cognitive behaviour therapies target modification of the behaviours and thoughts hypothesised to be maintaining a positive energy balance. Cognitive therapies target problematic thoughts hypothesised to be maintaining a positive energy balance (Cooper 2004; Fabricatore 2007). Third wave cognitive behaviour therapies are a family of interventions (e.g., meta‐cognitive therapy , acceptance and commitment therapy , mindfulness‐based cognitive therapy , dialectical behaviour therapy , and compassion‐focused therapy targeting modification of both behaviours and reactions to/relationships with thoughts hypothesised to be maintaining a positive energy balance (Öst 2008).

A range of other psychological interventions has been used in the treatment of overweight and obesity (Shaw 2005). These include relaxation therapy (Bertisch 2008), psychodynamic therapy (Wiltink 2007), hypnotherapy (Kirsch 1995), eye movement desensitisation and reprocessing (Stapleton 2011), emotion freedom techniques (Stapleton 2011), interpersonal psychotherapy (Tanofsky‐Kraff 2014), and emotion‐focused therapy (Compare 2013). Unfortunately the mechanism of action of these interventions in their treatment of obesity is not always explicitly and/or consistently defined.

Adverse effects of the intervention

The potential adverse effects of obesity interventions have received relatively little research attention (Shaw 2005; Shaw 2006). To date, the biological impacts of weight loss have been shown to be positive, demonstrating improvements in obesity‐related disease risk factors (e.g., improved insulin resistance) in the short‐ to medium‐term (Shaw 2005). Similarly, participation in a weight loss intervention has generally been shown to result in improvements in psychological outcomes (e.g., depression, disordered eating) in the short‐ to medium‐term (Hardeman 2000). Although some studies have found that these improvements are related to the amount of weight lost (Blaine 2007), others have attributed improvements to other factors such as the social support received while participating in a weight loss intervention (Elfhag 2005; McLean 2003). Despite widespread recognition of the negative social consequences of obesity (e.g., stigmatisation, discrimination), little is known about the effects of interventions on social outcomes (Papadopoulos 2015; Puhl 2003).

Why it is important to do this review

The high and increasing prevalence of overweight and obesity (WHO 2014), combined with the negative biopsychosocial comorbidities of excess weight (Guh 2009), and the limited effectiveness of prevention efforts to date (Lau 2007; Lemmens 2008; McTigure 2007; WHO 2000), highlight the need for effective overweight and obesity treatment. There is now a large and increasing body of evidence demonstrating the limited effectiveness of lifestyle interventions in achieving substantial and sustained weight loss (Shaw 2006; Wu 2009). In recognition of the challenges of achieving substantial and sustained weight loss, psychological interventions increasingly are included in treatment (Sarwer 2014; Shaw 2005).

The most recent Cochrane Review examining psychological interventions for overweight and obesity was published in 2005 (Shaw 2005). Over the last 10 years, the field has developed considerably on three fronts. First, the last decade has seen the development of 'third wave' psychological interventions (Öst 2008). Second, there has been a proliferation of research examining the efficacy, and more recently, the effectiveness of psychological interventions, particularly cognitive behavioural interventions (Hendrie 2012). Third, this research has considered a broader range of biopsychosocial outcomes and included longer follow‐up periods (Blaine 2007). As a result, a new review would include a broader range of psychological interventions and consider the impact of various treatment characteristics on treatment outcomes more comprehensively. Furthermore, a review of current literature would also help to clarify a series of inconsistent findings and interpretation of findings that are present in the literature. Although there have been a number of related systematic reviews of psychological interventions for overweight and obesity conducted since 2005, they have considered more specific questions such as methods of delivery of intervention (i.e., web‐based) (Neve 2010), specific populations (e.g., disabled) (Hamilton 2007), or specific types of psychotherapy (e.g., hypnosis) (Pittler 2005). Thus, there is a need for an updated and comprehensive review of psychological interventions for overweight and obesity.

Objectives

To assess the effects of psychological interventions for the treatment of overweight and obese adults. Specific objectives are to examine the efficacy of:

1. All psychological therapies versus minimal or no intervention;

2. All psychological therapies versus an active diet and/or exercise intervention;

3. Behavioural psychological therapies (first, second or third wave) versus other psychological interventions.

Secondary objectives are to examine if the magnitude of intervention effects (objectives 1, 2, and 3) for the primary outcome of BMI are modified by particular intervention characteristics (length of follow‐up), or participant characteristics (degree of excess weight). We also plan to investigate whether the effects of behavioural therapy are modified by the type of behaviour intervention (first, second or third wave).

Methods

Criteria for considering studies for this review

Types of studies

General info → Cite the protocol for the review. → Use past tense for the methods section. → If specific items could not be performed state 'we planned ..' or similar.

Types of studies

We included randomised controlled trials (RCTs), including cluster randomised trials.

Types of participants

We included trials of adult participants only (aged 18 to 65 years). Trials included adults who are overweight or obese according to any parameter (e.g. BMI, waist measurement, waist‐to‐hip ratio). Over the years, the diagnostic criteria and classification of obesity have changed several times (NHMRC 1997). To be consistent with changes in classification and diagnostic criteria of obesity over time, the diagnosis should have been established using the standard criteria valid at the time the trial commenced. Studies involving participants with comorbid physical or mental disorders will be eligible for inclusion as long as the primary focus of the intervention is weight loss. Trials may be conducted in primary care and community‐based settings, or in secondary or specialist settings and will include both professionally‐ and self‐referred participants.

Types of interventions

All trials stating that they include a psychological intervention will be included. There will be no restriction on who delivers the intervention. If multiple arms are included in a trial, any arm that meets the inclusion criteria will be included in the review.

We planned to investigate the following comparisons of intervention versus control/comparator.

• Psychological intervention versus minimal or no intervention

• Psychological intervention versus active diet, exercise intervention or both.

• Behavioural psychological therapies (first, second or third wave) versus other psychological interventions.

Comparisons of psychotherapy as a supplementary therapy will also be included if the additional effect of psychotherapy can be determined (e.g. exercise plus psychotherapy versus psychotherapy alone). Concomitant interventions will have to be the same in both the intervention and comparator groups to establish fair comparisons. If a trial includes multiple arms, we includeD any arm that meets the review inclusion criteria.

Minimum duration of intervention

We will define trial duration according to the number of months over which the trial has been conducted and will only include trials in the analyses with interventions that lasted longer than three months. Trials in which the intervention was of less than three months' duration will be listed in an 'Additional table' but not included in analyses.

Minimum duration of follow‐up

Minimal duration of follow‐up will be .... We will define extended follow‐up periods (open‐label extension studies) as follow‐up of participants once the original trial, as specified in the trial protocol, has been terminated.

Summary of specific exclusion criteria

• Trials in which the psychological intervention was not delivered in a face‐to‐face format (at least one face‐to‐face session) between the participant and therapist. However, we included studies of interventions in which face‐to‐face therapy was augmented by telephone‐ or Internet‐based support.

• Psychological interventions delivered solely by bibliotherapy, telephone or the Internet.

• Trials that combine a pharmacological intervention, a surgical intervention or both with a psychological intervention.

• Of interventions designed to prevent weight gain or to treat eating disorders.

Types of outcome measures

We will not exclude a trial if they fail to report one or several of our primary or secondary outcome measures. If the report none of our primary or secondary outcomes in the trial, we will not include the trial but provide some basic information in an additional table.

Primary outcomes

• Body mass index (BMI)

• Weight

• Adverse events

Secondary outcomes

• Indicator of body mass other than BMI or weight

• Cardiometabolic disease

• All‐cause mortality

• Health‐related quality of life (HrQoL)

• Psychological factors

Method and timing of outcome measurement

To be included, a trial must have a minimum follow‐up of 12 months from baseline. If multiple measures are available for a particular outcome, we will extract the measures closest to 12 months and 24 months for BMI or weight. For all other outcomes, we will extract the measure closest to 24 months.

• BMI: defined as weight (kg) divided by height (m) squared.

• Weight: weight in kg.

• Adverse event: any reported adverse event during intervention and follow‐up.

• Indicator of body mass other than BMI or weight: defined as waist measurement, waist‐to‐hip ratio.

• Cardiometabolic disease: defined as development of type 2 diabetes, coronary heart disease or stroke.

• All‐cause mortality: defined as death from any cause.

• HrQoL: evaluated by a validated instrument. If multiple outcomes of HrQoL are reported, weight‐specific HrQoL will be selected in preference to general HrQoL.

• Psychological factors: defined as depression, eating disorders, anxiety, self‐esteem. If multiple measures of psychological distress are included in a publication we will select the median of these measures for inclusion in the analyses.

Search methods for identification of studies

Electronic searches

We searched the following sources from inception of each database to the specified date and placed no restrictions on the language of publication.

• Cochrane Central Register of Controlled Trials (CENTRAL) via Cochrane Register of Studies Online (CRSO) (searched year, Issue .).

• MEDLINE Ovid (Epub Ahead of Print, In‐Process & Other Non‐Indexed Citations, Ovid MEDLINE(R) Daily and Ovid MEDLINE(R)) (from 1946 to month week year).

• PubMed (subsets not available on Ovid).

• PsycINFO.

• ClinicalTrials.gov (www.clinicaltrials.gov) (searched day month year).

• World Health Organization International Clinical Trials Registry Platform (ICTRP) (www.who.int/trialsearch/) (searched day month year).

For detailed search strategies, see Appendix 1. We continuously applied an email alert service for MEDLINE via OvidSP to identify newly published trials using the search strategy detailed in Appendix 1.

If we detected additional relevant key words during any electronic or other searches, we modified the electronic search strategies to incorporate these terms and documented the changes to the search strategy.

Searching other resources

We tried to identify other potentially‐eligible trials or ancillary publications by searching the reference lists of retrieved included trials, (systematic) reviews, meta‐analyses and health technology assessment reports. In addition we contacted authors of included trials to identify any further studies we may have missed.

Data collection and analysis

Selection of studies

Two review authors (LB, ME) independently scanned the abstract or title, or both, of every record retrieved by the literature searches, to determine which trials should be assessed further. We investigated all potentially‐relevant articles as full text. Full articles have been retrieved for further assessment if the information given suggests that the trial: (1) includes participants who are overweight or obese; (2) compares a psychological intervention to minimal or no intervention, an active diet and/or exercise intervention or another psychological intervention; and (3) uses random allocation to the comparison groups. If there was any doubt regarding these criteria from the information given in the title and abstract, the full article was retrieved for clarification.

We resolved any discrepancies through consensus or recourse to a third review author (LB). If resolution of a disagreement was not possible, we categorised the trial as a 'study awaiting classification' and we contacted the trial authors for clarification. We presented an adapted PRISMA flow diagram showing the process of trial selection (Liberati 2009). We listed all articles excluded after full‐text assessment in a 'Characteristics of excluded studies' table and provided the reasons for exclusion.

Data extraction and management

For trials that fulfil inclusion criteria, two review authors (ME, KM) independently abstracted key participant and intervention characteristics. We reported data on efficacy outcomes and adverse events using standardised data extraction sheets from the Cochrane Metabolic and Endocrine Disorders Group. We resolved any disagreements by discussion or, if required, by consultation with a third review author (LB).

We provided information about potentially relevant ongoing trials, including the trial identifiers, in the Characteristics of ongoing studies table and in the Appendix 5 ('Matrix of trial endpoint (publications and trial documents)'). We tried to find the protocol for each included trial and reported primary, secondary and other outcomes in comparison with data in publications in the Appendix 5.

We emailed all authors of included studies to enquire whether they would be willing to answer questions regarding their trials. We thereafter sought relevant missing information on the trial from the primary author(s) of the article, if required.

Dealing with duplicate and companion publications

In the event of duplicate publications, companion documents, or multiple reports of a primary trial, we maximised the information yield by collating all available data and we used the most complete dataset aggregated across all known publications. We listed duplicate publications, companion documents, multiple reports of a primary trial and trial documents of included trials (such as trial registry information) as secondary references under the trial identifier (ID) of the included trial. Furthermore, we also listed duplicate publications, companion documents, multiple reports of a trial and trial documents of excluded trials (such as trial registry information) as secondary references under the trial ID of the excluded trial.

Data from clinical trial registers

If data from included trials are available as study results in clinical trial registers such as ClinicalTrials.gov or similar sources, we made full use of this information and extract data. If there was also a full publication of the trial, we collated and critically appraised all available data. If an included trial was marked as a completed study in a clinical trial register but no additional information is available, we added this trial to the table 'Characteristics of studies awaiting classification'.

Assessment of risk of bias in included studies

Two review authors (ME, KM) independently assessed the risk of bias of each included trial. We resolved any disagreements by consensus, or by consultation with a third review author (JM). In cases of disagreement, we consulted the remainder of the review author team and make a judgement based on consensus. If adequate information was unavailable from the publications, trial protocols or other sources, we contacted the trial authors for more detail.

We used the Cochrane 'Risk of bias' assessment tool (Higgins 2011a; Higgins 2011b), assigning assessments of low, high or unclear risk of bias. We evaluated individual bias items as described in the Cochrane Handbook for Systematic Reviews of Interventions according to the criteria and associated categorisations contained therein(Higgins 2011b).

Random sequence generation (selection bias due to inadequate generation of a randomised sequence)

We described for each included trial the method used to generate the allocation sequence in sufficient detail to allow an assessment of whether it should produce comparable groups.

• Low risk of bias: sequence generation was achieved using computer random number generation or a random number table. Drawing of lots, tossing a coin, shuffling cards or envelopes, and throwing dice are adequate if performed by an independent person not otherwise involved in the trial. Use of the minimisation technique will be considered as equivalent to being random.

• Unclear risk of bias: insufficient information about the sequence generation process.

• High risk of bias: the sequence generation method was non‐random (e.g. sequence generated by odd or even date of birth; sequence generated by some rule based on date (or day) of admission; sequence generated by some rule based on hospital or clinic record number; allocation by judgement of the clinician; allocation by preference of the participant; allocation based on the results of a laboratory test or a series of tests; allocation by availability of the intervention).

Allocation concealment (selection bias due to inadequate concealment of allocations prior to assignment)

We described for each included trial the method used to conceal allocation to interventions prior to assignment and assessed whether intervention allocation could have been foreseen in advance of, or during recruitment, or changed after assignment.

• Low risk of bias: central allocation (including telephone, interactive voice‐recorder, web‐based and pharmacy‐controlled randomisation); sequentially numbered drug containers of identical appearance; sequentially‐numbered, opaque, sealed envelopes.

• Unclear risk of bias: insufficient information about the allocation concealment.

• High risk of bias: using an open random allocation schedule (e.g. a list of random numbers); assignment envelopes were used without appropriate safeguards; alternation or rotation; date of birth; case record number; any other explicitly unconcealed procedure.

We also evaluated trial baseline data to incorporate assessment of baseline imbalance into the 'Risk of bias' judgement for selection bias (Corbett 2014). Chance imbalances may also affect judgements on the risk of attrition bias. In the case of unadjusted analyses we distinguished between trials we rated as being at low risk of bias on the basis of both randomisation methods and baseline similarity, and trials we judged as being at low risk of bias on the basis of baseline similarity alone (Corbett 2014). We reclassified judgements of unclear, low or high risk of selection bias as specified in Appendix 2.

Blinding of participants and study personnel (performance bias due to knowledge of the allocated interventions by participants and personnel during the trial)

We evaluated the risk of detection bias separately for each outcome (Hróbjartsson 2013). We noted whether endpoints were self‐reported, investigator‐assessed or adjudicated outcome measures (see below).

• Low risk of bias: blinding of participants and key study personnel ensured, and unlikely that the blinding could have been broken; no blinding or incomplete blinding, but the review authors judge that the outcome is not likely to be influenced by lack of blinding.

• Unclear risk of bias: insufficient information about the blinding of participants and study personnel; the trial did not address this outcome.

• High risk of bias: no blinding or incomplete blinding, and the outcome is likely to be influenced by lack of blinding; blinding of trial participants and key personnel attempted, but likely that the blinding could have been broken, and the outcome is likely to be influenced by lack of blinding.

Blinding of outcome assessment (detection bias due to knowledge of the allocated interventions by outcome assessment)

We evaluated the risk of detection bias separately for each outcome (Hróbjartsson 2013). We noted whether endpoints were self‐reported, investigator‐assessed or adjudicated outcome measures (see below).

• Low risk of bias: blinding of outcome assessment ensured, and unlikely that the blinding could have been broken; no blinding of outcome assessment, but the review authors judge that the outcome measurement is not likely to be influenced by lack of blinding.

• Unclear risk of bias: insufficient information about the blinding of outcome assessors; the trial did not address this outcome.

• High risk of bias: no blinding of outcome assessment, and the outcome measurement is likely to be influenced by lack of blinding; blinding of outcome assessment, but likely that the blinding could have been broken, and the outcome measurement is likely to be influenced by lack of blinding.

Incomplete outcome data (attrition bias due to amount, nature or handling of incomplete outcome data)

We described for each included trial, and/or for each outcome, the completeness of data including attrition and exclusions from the analysis. We stated whether the trial reported attrition and exclusions, and reported the number pf participants included in the analysis at each stage (compared with the number of randomised participants per intervention/comparator groups). We also noted it the trial reported the reasons for attrition or exclusion and whether missing data were balanced across groups or were related to outcomes. We considered the implications of missing outcome data per outcome such as high dropout rates (e.g. above 15%) or disparate attrition rates (e.g. difference of 10% or more between trial arms).

• Low risk of bias: no missing outcome data; reasons for missing outcome data unlikely to be related to true outcome (for survival data, censoring unlikely to be introducing bias); missing outcome data balanced in numbers across intervention groups, with similar reasons for missing data across groups; for dichotomous outcome data, the proportion of missing outcomes compared with observed event risk not enough to have a clinically‐relevant impact on the intervention effect estimate; for continuous outcome data, plausible effect size (difference in means or standardised difference in means) among missing outcomes not enough to have a clinically‐relevant impact on observed effect size; appropriate methods, such as multiple imputation, were used to handle missing data.

• Unclear risk of bias: insufficient information to assess whether missing data in combination with the method used to handle missing data were likely to induce bias; the trial did not address this outcome.

• High risk of bias: reason for missing outcome data likely to be related to true outcome, with either imbalance in numbers or reasons for missing data across intervention groups; for dichotomous outcome data, the proportion of missing outcomes compared with observed event risk enough to induce clinically‐relevant bias in intervention effect estimate; for continuous outcome data, plausible effect size (difference in means or standardised difference in means) among missing outcomes enough to induce clinically‐relevant bias in observed effect size; ‘as‐treated’ or similar analysis done with substantial departure of the intervention received from that assigned at randomisation; potentially inappropriate application of simple imputation.

Selective reporting (reporting bias due to selective outcome reporting)

We assessed outcome reporting bias by integrating the results of the appendix 'Matrix of trial endpoints (publications and trial documents)' Boutron 2014; Jones 2015; Mathieu 2009), with those of the appendix ''High risk of outcome reporting bias according to ORBIT classification' (Kirkham 2010). This analysis formed the basis for the judgement of selective reporting.

• Low risk of bias: the trial protocol is available and all of the trial’s pre‐specified (primary and secondary) outcomes that are of interest in the review have been reported in the pre‐specified way; the study protocol is not available but it is clear that the published reports include all expected outcomes (ORBIT classification).

• Unclear risk of bias: insufficient information about selective reporting.

• High risk of bias: not all of the trial’s pre‐specified primary outcomes have been reported; one or more primary outcomes is reported using measurements, analysis methods or subsets of the data (e.g. subscales) that were not pre‐specified; one or more reported primary outcomes were not pre‐specified (unless clear justification for their reporting is provided, such as an unexpected adverse effect); one or more outcomes of interest in the review are reported incompletely so that they cannot be entered in a meta‐analysis; the trial report fails to include results for a key outcome that would be expected to have been reported for such a trial (ORBIT classification).

Other bias

• Low risk of bias: the trial appeared to be free of other sources of bias.

• Unclear risk of bias: insufficient information to assess whether an important risk of bias existed; insufficient rationale or evidence that an identified problem introduced bias.

• High risk of bias: had a potential source of bias related to the specific trial design used; has been claimed to have been fraudulent; had some other serious problem.

Summary assessment of risk of bias

We presented a 'Risk of bias' graph and a 'Risk of bias' summary figure.

We distinguished between self‐reported, investigator‐assessed and adjudicated outcome measures.

We defined the following outcomes as self‐reported.

• Health‐related quality of life

• Psychological factors

• Adverse events

• BMI

• Weight

• Indicators of body mass other than BMI and weight loss

We defined the following outcomes as investigator‐assessed.

• BMI

• Weight loss

• Indicators of body mass other than BMI and weight loss

• Cardiometabolic disease

• All‐cause mortality

• Adverse events

Risk of bias for a trial across outcomes: some 'Risk of bias' domains, such as selection bias (sequence generation and allocation sequence concealment), affect the risk of bias across all outcome measures in a trial. In case of high risk of selection bias, we will mark all endpoints investigated in the associated trial as being at high risk. Otherwise, we will not perform a summary assessment of the risk of bias across all outcomes for a trial.

Risk of bias for an outcome within a trial and across domains: we will assess the risk of bias for an outcome measure by including all entries relevant to that outcome (i.e. both trial‐level entries and outcome‐specific entries). We consider low risk of bias to denote a low risk of bias for all key domains, unclear risk to denote an unclear risk of bias for one or more key domains and high risk to denote a high risk of bias for one or more key domains.

Risk of bias for an outcome across trials and across domains: these are the main summary assessments that we will incorporate into our judgments about the quality of evidence in the 'Summary of findings' tables. We will define outcomes as at low risk of bias when most information comes from trials at low risk of bias, unclear risk when most information comes from trials at low or unclear risk of bias and high risk when a sufficient proportion of information comes from trials at high risk of bias.

Measures of treatment effect

For continuous outcomes measured on the same scale (e.g. body mass index (BMI)) we estimated the intervention effect using the mean difference (MD) with 95% confidence intervals (CI). For continuous outcomes measuring the same underlying concept (e.g. psychological distress) but using different measurement scales, we calculated the standardised mean difference (SMD). In trials where the standard deviation (SD) of the outcome was not available at follow‐up, or cannot be recreated (e.g. only the SD of change is reported), we standardised by the pooled baseline SD. Risk ratios (RR) with 99% CI were used to estimate intervention effects for dichotomous outcomes (cardiometabolic disease and all‐cause mortality). To aid interpretation, in our 'Summary of findings' table(s) we also presented risk differences for a range of control group rates (lowest, highest, and median of the observed control group rates).

Unit of analysis issues

In this review, unit of analysis issues are most likely to arise from i) trials with more than two intervention groups, ii) cluster randomised trials, and iii) trials with therapist clustering (arising through the organisation of the intervention with therapists treating multiple patients). If more than one comparison from the same trial was eligible for inclusion in the same meta‐analysis, we either combined groups to create a single pair‐wise comparison or appropriately reduce the sample size so that the same participants do not contribute data to the meta‐analysis more than once (splitting the 'shared' group into two or more groups). While this latter approach offers some solution to adjusting the precision of the comparison, it does not account for correlation arising from the same set of participants being in multiple comparisons (Higgins 2011c).

We attempted to re‐analyse cluster‐RCTs that have not appropriately adjusted for potential clustering of participants within clusters in their analysis.The variance of the intervention effects will be inflated by a design effect. Calculation of a design effect involves estimation of an intra‐cluster correlation (ICC). We obtained estimates of ICCs through contact with authors, or imputed them by using either estimates from other included trials that reported ICCs or external estimates from empirical research (e.g. Bell 2012).

In many psychological therapy trials, randomisation occurs at the participant level, but clustering arises from therapists treating multiple patients; variation in outcomes for participants treated by the same therapists may be smaller than for patients treated by different therapists (Walwyn 2010). The impact of not adjusting for this clustering will be overly precise estimates of the intervention effect, P values that are too small, and increased false positive conclusions that the intervention is effective.This form of clustering is less well recognised, and consequently, it is likely that many trials will not have adjusted for clustering. Further, few estimates of ICCs will be available. We therefore plan to examine the impact of clustering arising from nesting of participants within therapists using sensitivity analyses and the approach described above.

Dealing with missing data

We presented attrition rates for the primary outcomes of the review, BMI and weight loss, or an indicator of BMI or weight loss when these outcome measures are not available. Reported results may be based on observed case data, last observation carried forward (LOCF), some other ad hoc imputation approach, or multiple imputation. Results based on multiple imputation were selected in preference to other imputation approaches, and if not available, we sought results based on observed case data.The sample of participants on which the results are based were reported in the review (e.g. observed case, LOCF, multiple imputation). We also extracted information on the trial analytical approach, since different analytical approaches are valid under different assumptions about the missing data (Bell 2013). For the primary outcomes, we conducted sensitivity analyses to examine the robustness of the pooled intervention effect to missing data. In trials with missing summary statistics (e.g. SDs) we imputed these statistics using methods outlined in Hozo (Hozo 2005) and reported the assumptions we have made in the results tables.

Assessment of heterogeneity

We assessed heterogeneity visually by inspecting the overlap of CIs on the forest plots. We formally tested for heterogeneity using the Chi² test (using a significance level of α = 0.1), and quantify heterogeneity using the I² statistic (Higgins 2002). CIs for estimated values of I² were calculated using the non central Chi² approximation implemented in the module heterogi (Orsini 2006) in the statistical package Stata (StataCorp: Stata Statistical Software: Release 12. In. College Station, TX: StataCorp LP; 2011).

Assessment of reporting biases

Funnel plots and contour‐enhanced funnel plots were used to investigated if there was evidence of small study effects for the outcome BMI (Peters 2008; Sterne 2011). The Egger test for funnel plot asymmetry was applied if there are sufficient trials (at least 10 for a particular outcome) (Egger 1997). The test were implemented using the module metabias (Harbord 2009) in the statistical package Stata (StataCorp: Stata Statistical Software: Release 12. In. College Station, TX: StataCorp LP.; 2011).

Data synthesis

Estimates of intervention effect will be pooled using a random‐effects model, since we expected there would be diversity in the clinical populations and interventions. DerSimonian and Laird’s method of moments estimator were used to estimate between‐trial variance (DerSimonian 1986). We planned to also examine the robustness of the results to the meta‐analysis method by using the restricted maximum likelihood between‐trial variance estimator (Raudenbush 2009) and the Knapp and Hartung method to calculate the CI (Knapp 2003). We planned to fit prediction intervals in the presence of unexplained heterogeneity, providing a predicted range for the true intervention effect in a new trial (Riley 2011).

Subgroup analysis and investigation of heterogeneity

We planned to undertake subgroup analyses or random‐effects meta‐regression to investigate if the magnitude of intervention effect for the primary outcomes of BMI and weight loss is modified by the following intervention and participant factors.

• Long‐term weight loss is the goal of obesity interventions, however the majority of participants regain lost weight over time.

• Behavioural therapies can be further divided into first wave (behavioural), second wave (cognitive behavioural) and third wave (mindfulness, acceptance, metacognition) therapies. Each is based on a different conceptualisation of behavioural and cognitive factors and uses different behavioural and cognitive intervention strategies which may have different impacts on outcomes.

• Intervention effects are likely to be modified by the degree of participant excess weight (overweight versus obese) at baseline. Individuals who are obese have more weight to lose, and are likely to have more extreme comorbidities, so greater improvements may be expected in this group.

Therefore the following were considered in analyses.

• Length of follow‐up (12 versus 24 months).

• Type of behavioural intervention (first wave, second wave, third wave).

• Participant degree of excess weight (overweight versus obesity).

Sensitivity analysis

Sensitivity analyses were undertaken for the outcomes of BMI and weight loss including only the trials judged to be at a low risk of bias. Sensitivity analyses will be undertaken to examine the robustness of the pooled intervention effect to assumptions regarding our imputed ICCs, and missing SDs. We will pool only trials considered to be at a low risk of bias using the criteria outlined in Assessment of risk of bias in included studies. We only pooled published trials. Finally, we investigated the impact of choice of meta‐analytic model on the pooled intervention effect (random‐effects versus fixed‐effect), and the meta‐analysis method (DerSimonian and Laird random‐effects method versus restricted maximum likelihood between‐trial variance estimator and the Knapp and Hartung method to calculate the confidence interval). Trials with published results in ClinicalTrials.gov but without a paper publication were included in this analysis.

Summary of findings

We presented a summary of the evidence in a 'Summary of findings' table. This provided key information about the best estimate of the magnitude of the effect, in relative terms and as absolute differences, for each relevant comparison of alternative management strategies, numbers of participants and trials addressing each important outcome and a rating of overall confidence in effect estimates for each outcome. We created the 'Summary of findings' table based on the methods described in the Cochrane Handbook for Systematic Reviews of Interventions (Schünemann 2011) using Review Manager (RevMan 5.3) table editor (RevMan 2014). We reported the following outcomes, listed according to priority.

1. BMI

2. Weight

3. Cardiometabolic disease

4. All‐cause mortality

5. Health‐related quality of life

6. Psychological factors

7. Adverse events

We presented the overall quality of the evidence for each outcome specified under 'Types of outcome measures: Summary of findings' according to the GRADE approach, which takes into account issues related not only to internal validity (risk of bias, inconsistency, imprecision, publication bias) but also to external validity, such as directness of results. Two review authors (NN, NN) independently rated the quality of evidence for each outcome. Differences in assessment were solved by discussion or consultation with a third researcher (NN).

We included an appendix entitled 'Checklist to aid consistency and reproducibility of GRADE assessments', to help with standardisation of the 'Summary of findings' tables (Meader 2014). Alternatively, we used the GRADEpro Guideline Development Tool (GDT) software and presented evidence profile tables as an appendix (GRADEproGDT 2015). We presented results for the outcomes as described in the Types of outcome measures section. If meta‐analysis was not possible, we presented the results in a narrative format in the 'Summary of findings' table. We justified all decisions to downgrade the quality of trials using footnotes, and we make comments to aid the reader's understanding of the Cochrane Review where necessary.

Appendices

Appendix 1. Search strategies

Cochrane Library

1. [mh ^Obesity] 2. [mh ^“Obesity, Abdominal“] 3. [mh ^“Obesity, Morbid“] 4. [mh ^“Weight Loss“] 5. [mh ^Overweight] 6. (obes* or overweight):ti,ab,kw 7. (weight next (reduction or loss or control or management)):ti,ab,kw 8. {or #1‐#7} 9. [mh Psychotherapy] 10. [mh Counseling] 11. ((psycho* or behav*) near/3 (therap* or treatment* or intervention* or counsel* or support*)):ti,ab,kw 12. ((behavior* or behaviour* or motivation*) near/3 (activation or therap* or treatment* or intervention* or modification* or 13. contract* or program* or counsel*)):ti,ab,kw 14. (cognitiv* near/3 (therap* or treatment* or intervention* or control* or program*)):ti,ab,kw 15. (train* near/3 (autogenic or assertive* or mind or sensitivity or relax*)):ti,ab,kw 16. ((art or aversion or color or colour or conversion or group or insight or supportiv* or exposure or play) next (therap* or psychotherap*)):ti,ab,kw 17. ((acceptance* or "activity scheduling" or adlerian or brief or "client cent*" or commitment* or compassion* or conjoint or conversational or couples or dance or dialectic* or eclectic or (emotion* near/2 focus*) or existential or experiential or expressive or family or (focus* near/2 oriented) or gestalt or humanistic or imagery or implosive or integrative or interpersonal or marital or metacognitive or milieu or morita or "multi modal" or multimodal or music or narrative or "non directive" or nondirective or "non specific" or nonspecific or "object relations" or "personal construct" or "person cent*" or persuasion or "pleasant event*" or primal or "problem focused" or "problem solving" or "process experiential" or psychodynamic or "rational emotive" or reality or "reciprocal inhibition" or relationship* or relax* or reminiscence or restructuring or schema* or "self control*" or selfcontrol* or "short term" or sex or "social effectiveness" or "social skill*" or "socio environmental" or socioenvironmental or "solution focused" or "stress management" or tapping or "time limited" or transference or transtheoretical or validation) near/3 (therap* or psychotherap*)):ti,ab,kw 18. (abreaction or "acting out" or "age regression" or autosuggestion or "balint group*" or biofeedback or catharsis or "contingency management" or countertransference or "covert sensitization" or "eye movement desensiti*" or "crisis intervention" or distraction or "dream analysis" or "emotional freedom" or "emotional healing tech*" or "free association" or freudian or "functional analysis" or griefwork or "guided imagery" or hypnos* or hypnotherap* or jungian or kleinian or logotherap* or meditation* or "mental healing" or mindfulness or (paradoxic* next technique*) or psychoanaly* or psychodram* or "psycho educat*" or psychoeducat* or "psycho ped*" or psychoped* or "relaxation techni*" or rogerian or "role play*" or "self analysis" or "self esteem" or sociotherap* or (support* near/2 group*) or therapist or (therapeutic* next technique*) or "third wave" or "transactional analysis"):ti,ab,kw 19. {or #9‐#17} 20. #8 and #18

MEDLINE (Ovid SP)

1. Obesity/ 2. Obesity, Abdominal/ 3. Obesity, Morbid/ 4. Weight Loss/ 5. Overweight/ 6. (obes* or overweight).tw. 7. (weight adj (reduction or loss or control or management)).tw. 8. or/1‐7 9. exp Psychotherapy/ 10. exp Counseling/ 11. ((psycho* or behav*) adj3 (therap* or treatment* or intervention* or counsel* or support*)).tw. 12. ((behavio?r* or motivation*) adj3 (activation or therap* or treatment* or intervention* or modification* or contract* or program* or counsel*)).tw. 13. (cognitiv* adj3 (therap* or treatment* or intervention* or control* or program*)).tw. 14. (train* adj3 (autogenic or assertive* or mind or sensitivity or relax*)).tw. 15. ((art or aversion or colo?r or conversion or group or insight or supportiv* or exposure or play) adj (therap* or psychotherap*)).tw. 16. ((acceptance* or activity scheduling or adlerian or brief or client cent* or commitment* or compassion* or conjoint or conversational or couples or dance or dialectic* or eclectic or emotion* focus* or existential or experiential or expressive or family or focus* oriented or gestalt or humanistic or imagery or implosive or integrative or interpersonal or marital or metacognitive or milieu or morita or multimodal or multi modal or music or narrative or nondirective or non directive or nonspecific or non specific or object relations or personal construct or person cent* or persuasion or pleasant event* or primal or problem focused or problem solving or process experiential or psychodynamic or rational emotive or reality or reciprocal inhibition or relationship* or relax* or reminiscence or restructuring or schema* or self control* or selfcontrol* or short term or sex or social effectiveness or social skill* or socio environmental or socioenvironmental or solution focused or stress management or tapping or time limited or transference or transtheoretical or validation) adj3 (therap* or psychotherap*)).tw. 17. (abreaction or acting out or age regression or autosuggestion or balint group* or biofeedback or catharsis or contingency management or countertransference or covert sensitization or eye movement desensiti* or crisis intervention or distraction or dream analysis or emotional freedom or emotional healing tech* or free association or freudian or functional analysis or griefwork or guided imagery or hypnos* or hypnotherap* or jungian or kleinian or logotherap* or meditation* or mental healing or mindfulness or paradoxic* technique* or psychoanaly* or psycho analy* or psychodram* or psychoeducat* psycho educat* or psychoped* or psycho ped* or relaxation techni* or rogerian or role play* or self analysis or self esteem or sociotherap* or support* group* or therapist or therapeutic* technique* or third wave or transactional analysis).tw. 18. or/9‐17 19. 8 and 18 [20‐29: Cochrane Handbook 2008 RCT filter ‐ sensitivity maximizing version – without "drug therapy.fs."] 20. randomized controlled trial.pt. 21. controlled clinical trial.pt. 22. randomi?ed.ab. 23. placebo.ab. 24. randomly.ab. 25. trial.ab. 26. groups.ab. 27. or/20‐26 28. exp animals/ not humans/ 29. 28 not 27 30. 19 and 29 31. remove duplicates from 30

PsycINFO (Ovid SP)

1. Obesity/ 2. Overweight/ 3. Weight Loss/ 4. Weight Control/ 5. Obesity (Attitudes Toward)/ 6. (overweight or obes*).tw. 7. (weight adj (reduction or loss or control or management)).tw. 8. or/1‐7 9. exp Behavior Modification/ 10. exp Cognitive Techniques/ 11. exp Creative Arts Therapy/ 12. exp Milieu Therapy/ 13. exp Psychotherapy/ 14. exp Psychotherapeutic Techniques/ 15. exp Relaxation Therapy/ 16. exp Sociotherapy/ 17. exp Behavior Contracting/ 18. exp Mindfulness/ 19. exp Mind Body Therapy 20. exp Support Groups/ 21. ((psychol* or psychodynam* or psychosoci* or psycho‐soci* or psycho‐physi* or psychotherap*) adj3 (therap* or treatment* or intervention* or counsel* or support*)).tw. 22. ((behavio?r* or motivation*) adj3 (activation or therap* or treatment* or intervention* or modification* or contract* or program* or counsel*)).tw. 23. (cognitiv* adj3 (therap* or treatment* or intervention* or control* or program*)).tw. 24. (train* adj3 (autogenic or assertive* or mind or sensitivity or relax*)).tw. 25. ((art or aversion or colo?r or conversion or group or insight or supportiv* or exposure or play) adj (therap* or psychotherap*)).tw. 26. ((acceptance* or activity scheduling or adlerian or brief or client cent* or commitment* or compassion* or conjoint or conversational or couples or dance or dialectic* or eclectic or emotion* focus* or existential or experiential or expressive or family or focus* oriented or gestalt or humanistic or imagery or implosive or integrative or interpersonal or marital or metacognitive or milieu or morita or multimodal or multi modal or music or narrative or nondirective or non directive or nonspecific or non specific or object relations or personal construct or person cent* or persuasion or pleasant event* or primal or problem focused or problem solving or process experiential or psychodynamic or rational emotive or reality or reciprocal inhibition or relationship* or relax* or reminiscence or restructuring or schema* or self control* or selfcontrol* or short term or sex or social effectiveness or social skill* or socio environmental or socioenvironmental or solution focused or stress management or tapping or time limited or transference or transtheoretical or validation) adj3 (therap* or psychotherap*)).tw. 27. (abreaction or acting out or age regression or autosuggestion or balint group* or biofeedback or catharsis or contingency management or countertransference or covert sensitization or eye movement desensiti* or crisis intervention or distraction or dream analysis or emotional freedom or emotional healing tech* or free association or freudian or functional analysis or griefwork or guided imagery or hypnos* or hypnotherap* or jungian or kleinian or logotherap* or meditation* or mental healing or mindfulness or paradoxic* technique* or psychoanaly* or psychodram* or psychoeducat* or psychoped* or relaxation techni* or rogerian or role play* or self analysis or self esteem or sociotherap* or therapist or therapeutic* technique* or third wave or transactional analysis).tw. 28. or/9‐27 29. 8 and 28 [30:Eady 2008‐ PsycINFO search strategies filter ‐ BS version] 30. (control* or random*).tw. or exp Treatment/ 31. 29 and 30 32. limit 31 to ("0100 journal" or "0110 peer‐reviewed journal" or "0120 non‐peer‐reviewed journal" or "0130 peer‐reviewed status unknown" or "0400 dissertation abstract")

ICTRP Search Portal (Standard search)

obes* AND psycho* OR obes* AND behavio* OR obes* AND cognitiv* OR obes* AND counsel* OR obes* AND emotion* OR obes* AND hypno* OR obes* AND meditation* OR obes* AND mindfulness* OR overweight* AND psycho* OR overweight* AND behavio* OR overweight* AND cognitiv* OR overweight* AND counsel* OR overweight* AND emotion* OR overweight* AND hypno* OR overweight* AND meditation* OR overweight* AND mindfulness*

ClinicalTrials.gov (Expert search)

INFLECT EXACT "Interventional" [STUDY‐TYPES] AND INFLECT EXACT "Adult" [AGE‐GROUP] | obese OR obesity OR overweight OR "weight loss" OR "weight reduction" OR "weight control" OR "weight management" | psychotherapy OR psychotherapeutic OR psychotherapeutical OR psychological OR "acting out" OR "age regression" OR autogenic OR autosuggestion OR assertive OR art OR aversion OR abreaction OR acceptance OR "activity scheduling" OR adlerian OR balint OR behavioural OR behavioral OR behaviour OR behavior OR biofeedback OR dance OR dialectic OR distraction OR "dream analysis" OR catharsis OR color OR colour OR "contingency management" OR cognitive OR conversion OR countertransference OR "covert sensitization" OR "client centered" OR commitment OR compassion OR conjoint OR conversational OR counseling OR couples OR "crisis intervention" OR "eye movement" OR eclectic OR emotion OR emotional OR existential OR experiential OR expressive OR family OR "focus oriented" OR "free association" OR freudian OR "functional analysis" OR "group therapy" OR gestalt OR griefwork OR "guided imagery" OR humanistic OR hypnosis OR hypnotherapy OR insight OR implosive OR integrative OR interpersonal OR jungian kleinian OR logotherapy OR marital OR metacognitive OR milieu OR mind OR morita OR motivation OR motivational OR modification OR "multi modal" OR multimodal OR music OR meditation OR "mental healing" OR mindfulness OR narrative OR "non directive" OR nondirective OR "non specific" OR nonspecific OR "object relations" OR "personal construct" OR "person centered" OR persuasion OR play OR "pleasant event" OR primal OR "problem focused" OR "problem solving" OR psychodynamic OR "psycho dynamic" OR paradoxic OR paradoxical OR "psycho analysis" OR psychoanalysis OR psychodrama OR "psycho education" OR psychoeducation OR "psycho pedagogical" OR psychopedagogical OR "rational emotive" OR reality OR "reciprocal inhibition" OR relationship OR relaxation OR reminiscence OR restructuring OR rogerian OR "role play" OR "schema therapy" OR "self control" OR selfcontrol OR "sensitivity training" OR sex OR "social effectiveness" OR "social skills" OR "socio environmental" OR socioenvironmental OR "solution focused" OR "stress management" OR support OR supportive OR "self analysis" AND or AND "self esteem" AND or sociotherapy OR tapping OR "time limited" OR transference OR transtheoretical OR therapist OR "third wave" OR "transactional analysis" OR "validation therapy"

What's new

Date	Event	Description
26 March 2018	Amended	This protocol is withdrawn because continuous progress in this project could not be achieved.

Declarations of interest

*** TEXT WILL BE DELETED BEFORE PUBLICATION OF THE PROTOCOL ***

Review authors: please note possible conflicts of interests (http://community.cochrane.org/editorial‐and‐publishing‐policy‐resource/conflicts‐interest‐and‐cochrane‐reviews).

For example, 2.2.4. Cochrane Review author also an author on a study listed in the review:

"Cochrane authors who include primary studies (which they had conducted) in their Cochrane Review should declare this in the review in the ‘Declarations of interest’ section. Authors of primary studies should not extract data from their own study or studies. Instead, another author(s) or an editor(s) should extract these data, and check the interpretation against the study report and any available study registration details or protocol. Also, the relevant authorship of the primary studies should be disclosed in Cochrane's disclosure of potential conflicts of interest form and therefore the Cochrane Review."

Notes

This protocol is withdrawn because continuous progress in this project could not be achieved.

Withdrawn from publication for reasons stated in the review